Submission #1095403

#	Time	Username	Problem	Language	Result	Execution time	Memory
1095403		sitablechair	Cat Exercise (JOI23_ho_t4)	C++17	100 / 100	164 ms	47312 KiB

Main

#include<bits/stdc++.h>
#define ll long long
#define sz(x) (signed)x.size()
#define pb push_back
#define ff first
#define ss second
#define endl '\n'
#define For(i,l,r) for(int i=l;i<=r;i++)
#define ForD(i,l,r) for(int i=r;i>=l;i--)

using namespace std;

const int N=2e5+3;

int n,p[N],d[N],par[20][N];
int mxChild[N];
ll f[N],dp[N];
vector<int> g[N];
int find_set(int a) {
    return (f[a]<0?a:f[a]=find_set(f[a]));
}
void unite(int u,int v) {
    int a=find_set(u),b=find_set(v);
    if (a==b) return;
    if (f[a]>f[b]) swap(a,b);
    f[a]+=f[b];
    f[b]=a;
}
void predfs(int u,int p=0) {
    for(auto v: g[u])
        if (v!=p) {
            d[v]=d[u]+1;
            par[0][v]=u;
            For(i,1,18) par[i][v]=par[i-1][par[i-1][v]];
            predfs(v,u);
        }
}
int lca(int u,int v) {
    if (d[v]>d[u]) swap(u,v);
    int dd=d[u]-d[v];
    For(i,0,18)
        if (dd>>i&1) u=par[i][u];
    if (u==v) return u;
    ForD(i,0,18)
        if (par[i][u]!=par[i][v]) u=par[i][u],v=par[i][v];
    return par[0][u];
}
int dis(int u,int v) {
    return d[u]+d[v]-2*d[lca(u,v)];
}
int main() {
    cin.tie(0)->sync_with_stdio(0);
    cin >> n;
    For(i,1,n) cin >> p[i];
    For(i,1,n-1) {
        int u,v;
        cin >> u >> v;
        g[p[u]].pb(p[v]);
        g[p[v]].pb(p[u]);
    }
    f[1]=-1;
    dp[1]=0;
    mxChild[1]=1;
    predfs(1);
    For(i,2,n) {
        dp[i]=0;
        for(auto u: g[i]) {
            if (u>i) continue;
            dp[i]=max(dp[i],dp[mxChild[find_set(u)]]+dis(mxChild[find_set(u)],i));
        }
        f[i]=-1;
        for(auto u: g[i])
            if (u<=i) unite(i,u);
        mxChild[find_set(i)]=i;
    }
    cout << dp[n] << endl;
    return 0;
}

• Subtask 1: 7 / 7
• Subtask 2: 7 / 7
• Subtask 3: 7 / 7
• Subtask 4: 10 / 10
• Subtask 5: 20 / 20
• Subtask 6: 23 / 23
• Subtask 7: 26 / 26